The present invention relates to a power train device, and in particular to a power train device to be used for an electric vehicle or other type device which is driven by an electric motor, a reduction gear mechanism and a differential gear mechanism.
A conventional power train device is disclosed in FIG. 3 at page 8 of Second Volume Sections 10-20 of SYMPOSIUM PROCEEDINGS which is published by FORD MOTOR Co., at international EV symposium held in Sep. 27-30, 1992. The conventional device as shown in FIG. 9 has an electric motor 1, a reduction gear mechanism 2, a differential gear mechanism 3, an input shaft 4 cooperating with the output side (rotor) of the electric motor 1, an output shaft 5 cooperating with the input side (deferential case) of the differential gear mechanism 3, and a pair of drive shafts 6 and 7 cooperating with the output side (side gear) the differential gear mechanism 3. The input shaft 4 and the output shaft 5 are positioned coaxially around the drive shafts 6 and 7. The input shaft 4 and the output shaft 5 cooperate with each other via the reduction gear mechanism 2. The electric motor 1 is positioned in series with one side of the reduction gear mechanism 2 in the axial direction. The differential gear mechanism 3 is positioned in series with the other side of the reduction gear mechanism 2 in the axial direction.
However, in the conventional power train device, the electric motor 1 and the differential gear mechanism 3 are positioned in series with the reduction gear mechanism 2 in the axial direction, so that the space required for positioning the electric motor 1, the differential gear mechanism 3 and the reduction gear mechanism 2 becomes larger in the axial direction. When the conventional power train device is installed in a vehicle, as shown in FIG. 10c, there are several adverse effects to the vehicle, such as the joint angle of the drive shafts 6 and 7 becomes large, the conventional power train device is interferes with a chassis frame of the vehicle, etc.
Further, there is another conventional power train device disclosed in FIG. 11. This conventional power train device has an electric motor 1, two reduction gear mechanisms 2, a differential gear mechanism 3, and a pair of drive shafts 6 and 7. The output of the electric motor is supplied to the differential gear mechanism 3 and the two outputs of the differential gear mechanism 3 are conveyed to the drive shafts 6 and 7 via the two reduction gear mechanisms 2 respectively. In this conventional power train device, two reduction gear mechanisms are necessary which requires more space for accommodating the power train device.